Clinical Characteristics and Underlying Medical Conditions Among Hospitalized Children and Adult Patients With Seasonal Influenza

Background: Influenza is a respiratory infection that causes a wide range of symptoms, from mild symptoms to a significantly impaired disease.  Objective: This study aims to examine demographic characteristics, clinical features, and underlying medical conditions in children and adults hospitalized with laboratory-confirmed influenza. Methods: This was a retrospective comparative study on 333 adults and 102 children hospitalized with symptoms of acute respiratory tract infection and seasonal influenza confirmed by reverse transcription polymerase chain reaction (RT-PCR) in three university hospitals, in Qazvin City, Iran, during two influenza seasons (March 2017 and February 2019).  Findings: Most clinical manifestations of influenza were similar among adults. A significant difference was observed among the two groups in terms of 1) a greater proportion of male patients in children (66.7%) and female patients in adults (58.6%); 2) adults were more exposed to risk factors than children (median 1 vs. 0); 3) a greater proportion of children presenting influenza-related encephalopathy (38.2% vs. 26.7%) and upper respiratory signs compared to adults; 4) a greater proportion of adults presenting lower respiratory signs and symptoms compared to children. The most common underlying conditions were asthma and diabetes mellitus (DM) in adults and diabetes mellitus (DM) and cancer in children. The duration of hospitalization had a significant relationship with the number of risk factors (r=0.219, P<0.001). Conclusion: In summary, influenza-related encephalopathy and upper respiratory signs are more prevalent in children, and in contrast, adults are more likely to have underlying medical conditions than children with seasonal influenza.